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random: group entropy collection functions

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commit 92c653cf14400946f376a29b828d6af7e01f38dd upstream.

This pulls all of the entropy collection-focused functions into the
fourth labeled section.

No functional changes.

Cc: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jason A. Donenfeld 2022-02-11 12:53:34 +01:00 committed by Greg Kroah-Hartman
parent e9ff357860
commit f04580811d
1 changed files with 206 additions and 164 deletions
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370
drivers/char/random.c
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@ -1039,60 +1039,112 @@ static bool drain_entropy(void *buf, size_t nbytes)
return true;
}
struct fast_pool {
union {
u32 pool32[4];
u64 pool64[2];
};
unsigned long last;
u16 reg_idx;
u8 count;
};
/**********************************************************************
*
* Entropy collection routines.
*
* The following exported functions are used for pushing entropy into
* the above entropy accumulation routines:
*
* void add_device_randomness(const void *buf, size_t size);
* void add_input_randomness(unsigned int type, unsigned int code,
* unsigned int value);
* void add_disk_randomness(struct gendisk *disk);
* void add_hwgenerator_randomness(const void *buffer, size_t count,
* size_t entropy);
* void add_bootloader_randomness(const void *buf, size_t size);
* void add_interrupt_randomness(int irq);
*
* add_device_randomness() adds data to the input pool that
* is likely to differ between two devices (or possibly even per boot).
* This would be things like MAC addresses or serial numbers, or the
* read-out of the RTC. This does *not* credit any actual entropy to
* the pool, but it initializes the pool to different values for devices
* that might otherwise be identical and have very little entropy
* available to them (particularly common in the embedded world).
*
* add_input_randomness() uses the input layer interrupt timing, as well
* as the event type information from the hardware.
*
* add_disk_randomness() uses what amounts to the seek time of block
* layer request events, on a per-disk_devt basis, as input to the
* entropy pool. Note that high-speed solid state drives with very low
* seek times do not make for good sources of entropy, as their seek
* times are usually fairly consistent.
*
* The above two routines try to estimate how many bits of entropy
* to credit. They do this by keeping track of the first and second
* order deltas of the event timings.
*
* add_hwgenerator_randomness() is for true hardware RNGs, and will credit
* entropy as specified by the caller. If the entropy pool is full it will
* block until more entropy is needed.
*
* add_bootloader_randomness() is the same as add_hwgenerator_randomness() or
* add_device_randomness(), depending on whether or not the configuration
* option CONFIG_RANDOM_TRUST_BOOTLOADER is set.
*
* add_interrupt_randomness() uses the interrupt timing as random
* inputs to the entropy pool. Using the cycle counters and the irq source
* as inputs, it feeds the input pool roughly once a second or after 64
* interrupts, crediting 1 bit of entropy for whichever comes first.
*
**********************************************************************/
static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU);
static int __init parse_trust_cpu(char *arg)
{
return kstrtobool(arg, &trust_cpu);
}
early_param("random.trust_cpu", parse_trust_cpu);
/*
* This is a fast mixing routine used by the interrupt randomness
* collector. It's hardcoded for an 128 bit pool and assumes that any
* locks that might be needed are taken by the caller.
* The first collection of entropy occurs at system boot while interrupts
* are still turned off. Here we push in RDSEED, a timestamp, and utsname().
* Depending on the above configuration knob, RDSEED may be considered
* sufficient for initialization. Note that much earlier setup may already
* have pushed entropy into the input pool by the time we get here.
*/
static void fast_mix(u32 pool[4])
int __init rand_initialize(void)
{
u32 a = pool[0], b = pool[1];
u32 c = pool[2], d = pool[3];
size_t i;
ktime_t now = ktime_get_real();
bool arch_init = true;
unsigned long rv;
a += b; c += d;
b = rol32(b, 6); d = rol32(d, 27);
d ^= a; b ^= c;
for (i = 0; i < BLAKE2S_BLOCK_SIZE; i += sizeof(rv)) {
if (!arch_get_random_seed_long_early(&rv) &&
!arch_get_random_long_early(&rv)) {
rv = random_get_entropy();
arch_init = false;
}
mix_pool_bytes(&rv, sizeof(rv));
}
mix_pool_bytes(&now, sizeof(now));
mix_pool_bytes(utsname(), sizeof(*(utsname())));
a += b; c += d;
b = rol32(b, 16); d = rol32(d, 14);
d ^= a; b ^= c;
extract_entropy(base_crng.key, sizeof(base_crng.key));
++base_crng.generation;
a += b; c += d;
b = rol32(b, 6); d = rol32(d, 27);
d ^= a; b ^= c;
if (arch_init && trust_cpu && crng_init < 2) {
crng_init = 2;
pr_notice("crng init done (trusting CPU's manufacturer)\n");
}
a += b; c += d;
b = rol32(b, 16); d = rol32(d, 14);
d ^= a; b ^= c;
pool[0] = a; pool[1] = b;
pool[2] = c; pool[3] = d;
if (ratelimit_disable) {
urandom_warning.interval = 0;
unseeded_warning.interval = 0;
}
return 0;
}
/*********************************************************************
*
* Entropy input management
*
*********************************************************************/
/* There is one of these per entropy source */
struct timer_rand_state {
cycles_t last_time;
long last_delta, last_delta2;
};
#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
/*
* Add device- or boot-specific data to the input pool to help
* initialize it.
@ -1116,8 +1168,6 @@ void add_device_randomness(const void *buf, size_t size)
}
EXPORT_SYMBOL(add_device_randomness);
static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
/*
* This function adds entropy to the entropy "pool" by using timing
* delays. It uses the timer_rand_state structure to make an estimate
@ -1179,8 +1229,9 @@ void add_input_randomness(unsigned int type, unsigned int code,
unsigned int value)
{
static unsigned char last_value;
static struct timer_rand_state input_timer_state = { INITIAL_JIFFIES };
/* ignore autorepeat and the like */
/* Ignore autorepeat and the like. */
if (value == last_value)
return;
@ -1190,6 +1241,119 @@ void add_input_randomness(unsigned int type, unsigned int code,
}
EXPORT_SYMBOL_GPL(add_input_randomness);
#ifdef CONFIG_BLOCK
void add_disk_randomness(struct gendisk *disk)
{
if (!disk || !disk->random)
return;
/* First major is 1, so we get >= 0x200 here. */
add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
}
EXPORT_SYMBOL_GPL(add_disk_randomness);
void rand_initialize_disk(struct gendisk *disk)
{
struct timer_rand_state *state;
/*
* If kzalloc returns null, we just won't use that entropy
* source.
*/
state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
if (state) {
state->last_time = INITIAL_JIFFIES;
disk->random = state;
}
}
#endif
/*
* Interface for in-kernel drivers of true hardware RNGs.
* Those devices may produce endless random bits and will be throttled
* when our pool is full.
*/
void add_hwgenerator_randomness(const void *buffer, size_t count,
size_t entropy)
{
if (unlikely(crng_init == 0)) {
size_t ret = crng_fast_load(buffer, count);
mix_pool_bytes(buffer, ret);
count -= ret;
buffer += ret;
if (!count || crng_init == 0)
return;
}
/*
* Throttle writing if we're above the trickle threshold.
* We'll be woken up again once below POOL_MIN_BITS, when
* the calling thread is about to terminate, or once
* CRNG_RESEED_INTERVAL has elapsed.
*/
wait_event_interruptible_timeout(random_write_wait,
!system_wq || kthread_should_stop() ||
input_pool.entropy_count < POOL_MIN_BITS,
CRNG_RESEED_INTERVAL);
mix_pool_bytes(buffer, count);
credit_entropy_bits(entropy);
}
EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
/*
* Handle random seed passed by bootloader.
* If the seed is trustworthy, it would be regarded as hardware RNGs. Otherwise
* it would be regarded as device data.
* The decision is controlled by CONFIG_RANDOM_TRUST_BOOTLOADER.
*/
void add_bootloader_randomness(const void *buf, size_t size)
{
if (IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER))
add_hwgenerator_randomness(buf, size, size * 8);
else
add_device_randomness(buf, size);
}
EXPORT_SYMBOL_GPL(add_bootloader_randomness);
struct fast_pool {
union {
u32 pool32[4];
u64 pool64[2];
};
unsigned long last;
u16 reg_idx;
u8 count;
};
/*
* This is a fast mixing routine used by the interrupt randomness
* collector. It's hardcoded for an 128 bit pool and assumes that any
* locks that might be needed are taken by the caller.
*/
static void fast_mix(u32 pool[4])
{
u32 a = pool[0], b = pool[1];
u32 c = pool[2], d = pool[3];
a += b; c += d;
b = rol32(b, 6); d = rol32(d, 27);
d ^= a; b ^= c;
a += b; c += d;
b = rol32(b, 16); d = rol32(d, 14);
d ^= a; b ^= c;
a += b; c += d;
b = rol32(b, 6); d = rol32(d, 27);
d ^= a; b ^= c;
a += b; c += d;
b = rol32(b, 16); d = rol32(d, 14);
d ^= a; b ^= c;
pool[0] = a; pool[1] = b;
pool[2] = c; pool[3] = d;
}
static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
static u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
@ -1259,22 +1423,11 @@ void add_interrupt_randomness(int irq)
fast_pool->count = 0;
/* award one bit for the contents of the fast pool */
/* Award one bit for the contents of the fast pool. */
credit_entropy_bits(1);
}
EXPORT_SYMBOL_GPL(add_interrupt_randomness);
#ifdef CONFIG_BLOCK
void add_disk_randomness(struct gendisk *disk)
{
if (!disk || !disk->random)
return;
/* first major is 1, so we get >= 0x200 here */
add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
}
EXPORT_SYMBOL_GPL(add_disk_randomness);
#endif
/*
* Each time the timer fires, we expect that we got an unpredictable
* jump in the cycle counter. Even if the timer is running on another
@ -1324,73 +1477,6 @@ static void try_to_generate_entropy(void)
mix_pool_bytes(&stack.now, sizeof(stack.now));
}
static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU);
static int __init parse_trust_cpu(char *arg)
{
return kstrtobool(arg, &trust_cpu);
}
early_param("random.trust_cpu", parse_trust_cpu);
/*
* Note that setup_arch() may call add_device_randomness()
* long before we get here. This allows seeding of the pools
* with some platform dependent data very early in the boot
* process. But it limits our options here. We must use
* statically allocated structures that already have all
* initializations complete at compile time. We should also
* take care not to overwrite the precious per platform data
* we were given.
*/
int __init rand_initialize(void)
{
size_t i;
ktime_t now = ktime_get_real();
bool arch_init = true;
unsigned long rv;
for (i = 0; i < BLAKE2S_BLOCK_SIZE; i += sizeof(rv)) {
if (!arch_get_random_seed_long_early(&rv) &&
!arch_get_random_long_early(&rv)) {
rv = random_get_entropy();
arch_init = false;
}
mix_pool_bytes(&rv, sizeof(rv));
}
mix_pool_bytes(&now, sizeof(now));
mix_pool_bytes(utsname(), sizeof(*(utsname())));
extract_entropy(base_crng.key, sizeof(base_crng.key));
++base_crng.generation;
if (arch_init && trust_cpu && crng_init < 2) {
crng_init = 2;
pr_notice("crng init done (trusting CPU's manufacturer)\n");
}
if (ratelimit_disable) {
urandom_warning.interval = 0;
unseeded_warning.interval = 0;
}
return 0;
}
#ifdef CONFIG_BLOCK
void rand_initialize_disk(struct gendisk *disk)
{
struct timer_rand_state *state;
/*
* If kzalloc returns null, we just won't use that entropy
* source.
*/
state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
if (state) {
state->last_time = INITIAL_JIFFIES;
disk->random = state;
}
}
#endif
static ssize_t urandom_read(struct file *file, char __user *buf, size_t nbytes,
loff_t *ppos)
{
@ -1675,47 +1761,3 @@ struct ctl_table random_table[] = {
{ }
};
#endif /* CONFIG_SYSCTL */
/* Interface for in-kernel drivers of true hardware RNGs.
* Those devices may produce endless random bits and will be throttled
* when our pool is full.
*/
void add_hwgenerator_randomness(const void *buffer, size_t count,
size_t entropy)
{
if (unlikely(crng_init == 0)) {
size_t ret = crng_fast_load(buffer, count);
mix_pool_bytes(buffer, ret);
count -= ret;
buffer += ret;
if (!count || crng_init == 0)
return;
}
/* Throttle writing if we're above the trickle threshold.
* We'll be woken up again once below POOL_MIN_BITS, when
* the calling thread is about to terminate, or once
* CRNG_RESEED_INTERVAL has elapsed.
*/
wait_event_interruptible_timeout(random_write_wait,
!system_wq || kthread_should_stop() ||
input_pool.entropy_count < POOL_MIN_BITS,
CRNG_RESEED_INTERVAL);
mix_pool_bytes(buffer, count);
credit_entropy_bits(entropy);
}
EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
/* Handle random seed passed by bootloader.
* If the seed is trustworthy, it would be regarded as hardware RNGs. Otherwise
* it would be regarded as device data.
* The decision is controlled by CONFIG_RANDOM_TRUST_BOOTLOADER.
*/
void add_bootloader_randomness(const void *buf, size_t size)
{
if (IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER))
add_hwgenerator_randomness(buf, size, size * 8);
else
add_device_randomness(buf, size);
}
EXPORT_SYMBOL_GPL(add_bootloader_randomness);